I just added one to my 84..metal roof, not a westie.
   Stuck the magnetic antenna end right up on the center/front of the roof.
Ran the wire forward, then down and used that little sticky 'wire fairing'
that came with the kit to cover the wire between the round antenna and the
windshield.  (Just a few inches)  There, I tucked it under the rubber trim,
using a putty knife and a dull screwdriver to push it under the edge of the
windshield rubber.  Be careful with the tools.. you may break the glass, but
you don't really have to push the wire that far under that molding..
  I ran that wire that way, across to the passengers side door, and came
around the "corner" right (out from under the window gasket onto the
A-pillar) at the end of my rain gutter..Right there, I drilled a real small
hole and secured the antenna wire with a little teenie wire tie.  Inside the
door jam, I used some brown tape..but that is probably overkill.  Then I
went back under the window rubber inside (A-pillar of the windshield) and
again with care, buried the wire under the molding as I routed it  down to
the dash..At the bottom corner of the windshield, you can finess the wire
behind the dash and you are home free to route it to wherever you stick the
radio "head"

  So, not the neatest install ever, but sheesh, it's a Vanagon and a few
inches of outdoor wire exposed as it goes around the A-pillar is not
stressing me out...I could probably do a better cleaner job in a full day or
two, with soldering iron and drills, but I have other things to obsess on...
  Don Hanson